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Re: [PATCH] Improve EXPLAIN ANALYZE overhead by sampling

From: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
To: Martijn van Oosterhout <kleptog(at)svana(dot)org>
Cc: pgsql-patches(at)postgresql(dot)org, Simon Riggs <simon(at)2ndquadrant(dot)com>
Subject: Re: [PATCH] Improve EXPLAIN ANALYZE overhead by sampling
Date: 2006-05-11 23:37:03
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Lists: pgsql-hackerspgsql-patches
On Tue, May 09, 2006 at 10:37:04PM +0200, Martijn van Oosterhout wrote:
> Note that the resulting times still include the overhead actually
> incurred, I didn't filter it out. I want the times to remain reflecting
> reality as closely as possible.
If we actually know the overhead I think it'd be very useful at times to
be able to remove it, especially if you're actually trying to compare to
the planner estimates. Maybe worth adding an option to the command?

> - I also didn't make it optional. I'm unsure about whether it should be
> optional or not, given the number of cases where it will make a
> difference to be very few.

The real question is how important it is to have the real data in the
cases where it would make a difference, and I suspect we can't answer
that until this is out in the field. It *might* be worth a #define or
some other way to disable it that doesn't require patching code, but
probably not.
Jim C. Nasby, Sr. Engineering Consultant      jnasby(at)pervasive(dot)com
Pervasive Software    work: 512-231-6117
vcard:       cell: 512-569-9461

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